Was going to use some rod I have but it was not a tight fit in the bore. Delrin also is terrible to cut with a hacksaw or drill as it is fairly soft and blades and the drill wanders. Used 3 drills in increasing sizes up to 4.5mm to keep the hole centralised to where it had to be. Worked great, the rifle groups well. Found that wood files are best for filing Delrin, give a better finish.
Baz
BE AN INDEPENDENT THINKER, DON'T FOLLOW THE CROWD
Inspired that - well done!
ASM
I am a Man of La Northumberlandia, a true Knight and spend my days on my Quest (my duty nay privilege!) and fighting dragons and unbeatable foe, to right the unrightable wrongs, to bear with unbearable sorrow and dreaming my impossible dreams.
BE AN INDEPENDENT THINKER, DON'T FOLLOW THE CROWD
I remember having one of these in .22 new in around 1963. Although I thought it was a grand little rifle at the time it didn't last long. After a few months the fore-end split, I was heart broken but my old scout master fixed it by inletting a couple of brass plates and screwing and gluing it together.
The loading port was also the rear sight, it was made of something like black nylon, it got progressively harder the push down once the pellet was inserted, so much so that I resorted to using something hard to press it down.
This flattened the top of the sight, the stock split again and the game was up. I've not seen one since but only recently I came across a bit of the underlever mechanism when I was cleaning out my old Dads shed, no idea what happened to the rest of it.
Sounds like you have improved on the original design. Would be interesting to see what one would be like if you made a similar design up from bits of a BSA Cadet and some mild steel. Heavier, but 5 ft/lbs would be nice.